(function flexible(window, document) {
	var docEl = document.documentElement;
	var dpr = window.devicePixelRatio || 1;

	// adjust body font size
	function setBodyFontSize() {
		if (document.body) {
			document.body.style.fontSize = (12 * dpr) + 'px';
		} else {
			document.addEventListener('DOMContentLoaded', setBodyFontSize);
		}
	}
	setBodyFontSize();

	// set 1rem = viewWidth / 10
	function setRemUnit() {
		var rem = docEl.clientWidth / 10;
		docEl.style.fontSize = rem + 'px';
	}

	setRemUnit();

	// reset rem unit on page resize
	window.addEventListener('resize', setRemUnit);
	window.addEventListener('pageshow', function(e) {
		if (e.persisted) {
			setRemUnit();
		}
	});

	// detect 0.5px supports
	if (dpr >= 2) {
		var fakeBody = document.createElement('body');
		var testElement = document.createElement('div');
		testElement.style.border = '.5px solid transparent';
		fakeBody.appendChild(testElement);
		docEl.appendChild(fakeBody);
		if (testElement.offsetHeight === 1) {
			docEl.classList.add('hairlines');
		}
		docEl.removeChild(fakeBody);
	}
}(window, document));